1. Field of Invention
This invention relates to automotive interior trim articles containing a panel structure mountable in an automobile vehicle to form a part of the interior thereof, and in particular to automobile interior trim articles such as instrument panels, door panels, and glove compartment doors. This invention further relates to a process for making automotive interior trim articles.
2. Description of Related Art
Automotive interior trim articles such as instrument panels, door panels, armrests, headrests, floor consoles, knee bolsters, and glove compartment doors conventionally have been constructed by applying a soft decorative covering over a rigid substrate mountable in an automobile vehicular body, with a cellular polyurethane padding interposed between the decorative covering and rigid substrate. A predetermined texture and color is usually provided to the decorative covering in an effort to simulate the appearance and feel of authentic leather.
The preparation of a self-supporting synthetic automotive interior trim article having a dual layer decorative covering is disclosed in U.S. Pat. No. 5,662,996 (corresponding to WO 93/23237), and in particular at Example 2 thereof. In accordance with the method disclosed in the Recticel ""996 patent for preparing this interior trim article, a solvent-based polyurethane lacquer is initially applied to an open mold surface as an xe2x80x9cin-mold paintxe2x80x9d, and then is dried by evaporating off the solvent. A xe2x80x9cskinxe2x80x9d prepared from a two-part polyurethane elastomer is thereafter formed on the inner surface of the dried in-mold paint by employing specialized nozzles and application systems. In practice, suitable spray nozzles and systems that can be employed are disclosed in U.S. Pat. Nos. 5,028,006 and 5,071,683. Next, a polyurethane cellular foam layer is prepared by spraying a polyurethane reaction mixture against the polyurethane elastomer skin. Finally, a polyurethane or polyisocyanurate reaction mixture is applied against the opposing surface of the polyurethane cellular foam layer to obtain a rigid synthetic carrier.
It appears that the commercial merit of this related art dual layer covering containing the in-mold paint disclosed in the Recticel ""996 patent, and the process for making the same, is negligible, as indicated by the current lack of commercial activity of this dual layer covering by Recticel. Recticel does not utilize an in-mold solvent-based lacquer in its own commercial activity. Recticel has even proscribed at least one of its customers from using its in-mold paint.
Further, the use of the solvent-based lacquer as the in-mold paint plagues the preparatory method disclosed in the Recticel ""996 patent with several complications and inefficiencies. For example, these lacquers contain large amounts of atmosphere-polluting volatile organic compounds (VOCs). Due to the extremely flammable and explosive nature of VOCs, such lacquers are subject to strict governmental regulations. Compliance with these governmental regulations often requires additional and expensive equipment designed to ensure worker safety and to protect against environmental pollution. For example, manufacturing facilities equipped for handling such lacquers must include special spray equipment, separate and customized spraying zones, and air cleansing equipment. Workers must also dress in special protective and often bulky and cumbersome gear that is fire resistant and shields against exposure to noxious fumes.
A need therefore exists to provide a process for making a panel structure containing a multi-layered decorative covering in which the panel structure can be produced in a more environmentally-friendly, efficient, and cost effective manner, and in which the resulting panel structure still has a desired high quality, leather-like appearance.
It is, therefore, an object of the present invention to solve the aforementioned problems associated with the related art as well as the need expressed above. In accordance with the principles of the present invention, this object is attained by providing a process for making a panel structure mountable on an automobile vehicle to form a part of the vehicle interior. The panel structure comprises a layered composite structure and a reinforcing substrate, with the substrate being hidden from the vehicle interior when the panel structure is mounted in the automobile. The layered composite structure comprises an outer layer defining at least a portion of an at least partially-exposed exterior surface of the panel structure and an inner layer.
According to one embodiment of this process, at least the following steps are performed to prepare the panel structure. At least one water-dispersed composition comprising at least one light-stable thermoplastic polyurethane (preferably in the form of resin particles in a colloid solution dispersed in water) containing one or more pendent hydroxyl and/or carboxyl functional groups, at least one desired coloring agent, and at least one light-stable, blocked, heat-activated diisocyanate is applied onto a heated mold surface shaped to define a complementary configuration to the outer layer. The light-stable thermoplastic polyurethane and the blocked, heat-activated diisocyanate are heated, preferably by pre-heating the mold surface, and reacted to induce crosslinking of the thermoplastic polyurethane with the blocked, heat-activated diisocyanate. Then, the water-dispersed composition is substantially dried while on the mold surface to coalesce the resin particles into a contiguous film and thereby form the exposed outer layer. Next, a rapidly reacting composition containing at least one aromatic polyisocyanate and at least one polyol is sprayed onto an inner surface of the outer layer while on the mold surface to form the inner layer comprising an aromatic polyurethane elastomer crosslinked with the polyurethane of the outer layer via residual unreacted functional groups of the blocked, heat-activated diisocyanate in the outer layer. Consequently, interfacial chemical bonding is obtained between the inner surface of the outer layer and an adjacent surface of the inner layer to form the layered composite structure. The layered composite structure is then united with the reinforcing substrate so that the reinforcing substrate serves to reinforce the outer layer. Optionally, a soft cellular polyurethane foam layer can be formed intermediate the inner layer and the reinforcing substrate. Consequently, the panel structure retains the touch, color and configuration of the exposed portion and the compressing feel provided to the outer layer by the inner layer and the optional soft cellular foam intermediate layer.
Another object of the present invention is the provision of an automotive interior trim article containing a panel structure made by the method of the present invention, and in particular the provision of a panel structure having an exterior surface which simulates the appearance and feel of authentic leather.
In accordance with the principles of the present invention, this object is attained by providing an article comprising a panel structure mountable in an automobile vehicle to form a part of the interior thereof. The panel structure has an exterior surface at least partially exposed to the vehicle interior and an interior surface which is hidden from the vehicle interior when the panel structure is mounted to the automobile vehicle structure. The panel structure comprises a reinforcing substrate and layered composite structure, with a soft cellular polyurethane foam layer optionally interposed therebetween. The reinforcing substrate has one surface defining the interior surface of the panel structure, and an opposite surface which is united to the layered composite structure. The layered composite structure comprises an outer layer and an inner layer. The outer layer defines at least a portion of the exposed exterior surface of the panel structure, and has the desired touch, color, and configuration of the panel structure, as well as exhibiting good chemical resistance. The outer layer comprises a substantially dried, light-stable, crosslinked polyurethane formulated from a water-dispersed composition comprising at least one desired coloring agent, at least one light-stable thermoplastic polyurethane containing one or more pendent hydroxyl and/or carboxyl functional groups, and a light-stable, blocked, heat-activated diisocyanate cross-linker. The light-stable aliphatic thermoplastic polyurethane and the blocked, heat-activated diisocyanate are heated to thereby produce a crosslinking reaction and molded on a heated mold surface shaped to define a complementary configuration to the outer layer, and then are dried on the mold surface. The inner layer, which is thicker than the outer layer, comprises an aromatic polyurethane elastomer formulated from a rapidly reacting composition containing at least one aromatic polyisocyanate and at least one polyol. The blocked, heat-activated diisocyanate serves to crosslink the aromatic polyurethane elastomer with the light-stable polyurethane of the outer layer. Consequently, the inner layer has a surface adjacent to and interfacially chemically bonded with an inner surface of the outer layer. The interfacial chemical bonds are formed by spraying the rapidly reacting composition onto the inner surface of the outer layer while the outer layer is retained on the mold surface. The reinforcing substrate serves to reinforce the outer layer while retaining the touch and color of the exposed portion and the compressing feel provided to the outer layer by the inner layer and the optionally interposed soft cellular polyurethane foam.
The composite provided in accordance with this embodiment exhibits excellent chemical, scuff and mar resistance to external influences. These and other properties are further enhanced by the selection of an aromatic polyisocyanate, as opposed to an aliphatic polyisocyanate, for making the polyurethane inner layer. Physical properties exhibited by and the processability of aromatic-based elastomers exceed those of aliphatic-based elastomers in several categories that are crucial in the automobile industry. For example, the improved processability of the aromatic-based elastomers is manifested by their better sprayability, reduced run-back, faster cure rates and demolding times, excellent handling, fewer pin holes, and more uniform thicknesses. The aromatic-based elastomers also exhibit higher tensile and tear strengths, better elongation and xe2x80x9ccold flexxe2x80x9d capability, and lower cost than their aliphatic-based counterparts. These characteristics translate into faster production times and higher quality products than could be attained with aliphatic-based elastomers. Moreover, concerns over the aromatic-based elastomer becoming less stable after prolonged exposure to light are obviated, since the light-stable polyurethane outer layer masks the aromatic-based elastomer from direct exposure to sunlight.
Further, appropriate additives can be introduced into the composite to provide the composite with the non-reflective and low gloss surface appearance desired for such panel structures. Furthermore, both the inner and outer layers of the composite are characterized by excellent extensibility, such that the composite can withstand indentation and flexure during use without causing cracking in the outer layer over a wide temperature range, such as from xe2x88x9230xc2x0 C. to 120xc2x0 C.
The principles of the present invention enunciated above are applicable to all types of panel structures, but have particular applicability to instrument panels (also referred to as dashboards) and door panels. Moreover, the principles of the present invention are applicable to various types of vehicles, including passenger cars, trucks, vans, utility vehicles, and others.
These and other objects, features, and advantages of the present invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the present invention.